Air temperature and humidity measurement is essential for environmental monitoring and energy management system in mission critical facilities. These systems usually need large amount of sensors in real time measurement. There are two types of sensors for these systems, wired or wireless. Conventional sensors are wired, which rely on physical wires to provide continuous power supply and transmit data to the data acquisition system. However, wired sensors and systems take a long time for installation and their reliability is dependent on a power supply. There are a small number of battery powered wireless temperature and humidity sensors in the market. They utilize wireless technologies like WIFI, ZigBee or sub-1 G MHz systems to transmit data. These wireless sensors have relatively short transmission distances, from 20 meters to 100 meters at open space. Their battery life is also typically short from 1 to 5 years. Although there are a couple of products that claim that their battery life is more than 10 years, these sensors are bulky and their transmission distance is short.